Identification of an 8-vinyl reductase involved in bacteriochlorophyll biosynthesis in Rhodobacter sphaeroides and evidence for the existence of a third distinct class of the enzyme

被引:23
|
作者
Canniffe, Daniel P. [1 ]
Jackson, Philip J. [1 ,2 ]
Hollingshead, Sarah [1 ]
Dickman, Mark J. [2 ]
Hunter, C. Neil [1 ]
机构
[1] Univ Sheffield, Dept Mol Biol & Biotechnol, Sheffield S10 2TN, S Yorkshire, England
[2] Univ Sheffield, ChELSI Inst, Dept Chem & Biol Engn, Sheffield S1 3JD, S Yorkshire, England
基金
英国生物技术与生命科学研究理事会;
关键词
bacteriochlorophyll biosynthesis; chlorophyll; photosynthesis; Rhodobacter sphaeroides; Synechocystis sp PCC6803; 8-vinyl reductase; PERFORMANCE LIQUID-CHROMATOGRAPHY; SYNECHOCYSTIS SP PCC6803; CHLOROPHYLL BIOSYNTHESIS; ARABIDOPSIS-THALIANA; DIVINYL PROTOCHLOROPHYLLIDE; RHODOPSEUDOMONAS-CAPSULATA; CHLOROPLAST BIOGENESIS; ESCHERICHIA-COLI; SULFUR BACTERIA; CLONING VECTORS;
D O I
10.1042/BJ20121723
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The purple phototrophic bacterium Rhodobacter sphaeroides utilises bacteriochlorophyll a for light harvesting and photochemistry. The synthesis of this photopigment includes the reduction of a vinyl group at the C8 position to an ethyl group, catalysed by a C8-vinyl reductase. An active form of this enzyme has not been identified in R. sphaeroides, but its genome contains two candidate ORFs (open reading frames) similar to those reported to encode C8-vinyl reductases in the closely related Rhodobacter capsulatus (bchJ), and in plants and green sulfur bacteria (rsp_3070). To determine which gene encodes the active enzyme, knock-out mutants in both genes were constructed. Surprisingly, mutants in which one or both genes were deleted still retained the ability to synthesize C8-ethyl bacteriochlorophyll. These genes were subsequently expressed in a cyanobacterial mutant that cannot synthesize C8-ethyl chlorophyll a. R. sphaeroides rsp_3070 was able to restore synthesis of the WT (wild-type) C8-ethyl chlorophyll a in the mutant, whereas bchJ did not. The results of the present study demonstrate that Rsp_3070 is a functional C8-vinyl reductase and that R. sphaeroides utilises at least two enzymes to catalyse this reaction, indicating the existence of a third class, while there remains no direct evidence for the activity of BchJ as a C8-vinyl reductase.
引用
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页码:397 / 405
页数:9
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